Closure with a molded ring gasket



' Dec. 26, 1967 Filed Oct. 25, 1965 v l3 4 7 Z 1 20 m /\k' fi 7 i I v I I9 L l8 v 7 R. c. OWEN 3,360,148 CLOSURE WITH A MOLDED RING GASKET I M INVENTOR 22 RONALD C- OWEN ATT'YS United States Patent 3,360,148 CLOSURE WITH A MOLDED RING GASKET Ronald C. Owen, Harwood Heights, Ill., assignor to Continental Can Company, Inc., New York, N.Y., a corporation of New York Filed Oct. 23, 1965, Ser. No. 502,999 2 Claims. (Cl. 215-40) ABSTRACT OF THE DISCLOSURE A closure cap having a molded gasket with a portion of reduced thickness at its inner periphery, which portion terminates in a sharply defined raised bead to form a flash free cutoff of the gasket. A method of molding the gasket and the molding punch used are also disclosed.

This invention relates to a closure and method of manufacturing the same. More specifically, the present invention is directed to a novel gasket design having a flash free, sharply defined termination of the gasket material at the inner margin after it has been molded or shaped to the desired cross sectional configuration.

One problem experienced in the production of molded or shaped gaskets was that of terminating the gasket material along a sharply defined line or in a flash free manner. In those gasket designs wherein the outer peripheral margin was not confined during shaping, flashing still occurred at the inner peripheral margin with its adverse effects on the appearance of the finished product.

The present invention relates to a novel gasket design and method of forming the same which permits the rapid flash free production of molded type gaskets for closure caps and like applications. In practicing the invention, a novel shaping punch is provide-d to form a sharply defined or flash free termination of-the gasket material at the inner peripheral margin.

A better understanding of the salient features of the present invention and a preferred method of practicing the same will become apparent when a consideration is given to the objects achieved.

It is an object of this invention to provide a new and improved molded gasket having a sharply defined flash free inner margin.

It is a further object of this invention to provide a new and improved method of manufacturing a molded gasket for a closure cap.

It is a still further object of this invention to provide a new and improved closure cap having a molded gasket terminating in a flash free inner marginal head portion which assists in anchoring a main body portion of the gasket to the closure shell. 7

It is a further object of this invention to provide a novel shaping punch for use in the rapid formation of flash free gaskets.

Additional objects other than those specifically enumerated will become apparent in the course of the following description of a preferred embodiment and method while other modifications and methods will become clearly apparent to the man in the art who reads the description and studies the drawings.

FIG. 1 is a diametric cross section of a closure cap having a ring of unshaped gasket compound deposited therein;

FIG. 2 is a cross sectional view of the cap of FIG. 1 supported on a platen and shaped by a punch shown fragmentarily; and

FIG. 3 is an enlarged view of the encircled portion 3 of FIG. 2.

Referring now to FIG. 1, reference character 10 indicates a closure shell having a flat top panel 11 and skirt 12 which may be terminated in a rolled edge 13. The rolled edge 13 may be flattened as at 14 to form retainer lugs for co-operation with lugs, threads or the like on a container finish. Any suitable form of retention means may be used in lieu of that illustrated. The top panel may have a depressed stacking panel portion 15 adjacent the outer margins to permit stacking of containers thereon during display of the finished package.

Outwardly of the stacking panel is formed an annular gasket groove 16 which has a flat bottom 17 merging at its outer periphery with an axially directed wall 18 which is joined to a portion of increased diameter 20 through a radial wall portion 19. Disposed within the channel or gasket groove 16 is a measured amount of plastomeric material 21 which is metered into the groove in a manner to be described below. While the gasket material is shown as having an arcuate cross sectional configuration, it may take any shape or form which would naturally occur when placed in the shell 10 for subsequent shaping.

In the illustrated form, the annular layer of gasket compound 21 has been deposited in the shell 10 by a fixed nozzle located above the shell 10 while the latter is rotating at approximately 600 to 1,500 rpm. on a suitable work holder. The nozzle may have an orifice from about 0.040 to 0.100 inch in diameter and is located sufficiently close to the shell 10 to cause adherence of the gasket material 21 to the usual coating on the shell upon release from the nozzle.

The gasket material may be formed of a moldable compound such as a plastomeric composition of vinyl resin particles, plasticizer and lubricant, and is essentially insoluble at room temperature or the temperature of application which may be up to about F. The plastomeric material is placed in the annular gasket groove 16 adjacent the outer peripheral portion of the shell 10 and is so located whereby it will co-operate with a molding or shaping punch in the manner shown in FIG. 2. The viscosity of the material is such that it is relatively stable and retains the shape assumed after placement in the shell 10 at least until the molding or shaping step is initiated.

In FIG. 2, a platen 22 is provided with a shell supporting surface which engages the stacking panel and also provides continuous support beneath the gasket groove 16. A novel molding or shaping punch 24 is providel with a gasket forming groove 26 adjacent its outer margin which groove may assume any desired configuration suitable for co-operation with the container finish to which the cap is applied. In the present design, the gasket forming surface 25 is of a generally flat frustoconical design having a relieved outer margin 26 which, in the final position, is spaced from the 'arcuate portion joining the radially extending wall portion 19 and axially directed wall 18 forming one side of the gasket groove 16. The molding punch 24 may be heated by suitable means to a temperature of the order of 275-400 F. while the platen 22 may be heated by any suitable means such as an open flame 27 or an indirect heating means to elevate it to a temperature of from about 275 F. to about 350 F. Variations made within the specified temperature ranges will provide an optimum shaping time for the specific gasket compound used.

As seen in FIG. 3, the punch 24 is provided with gasket forming surfaces 25 and 26, the latter forming a rounded outer periphery 32 on the gasket. The frusto-conical or inwardly tapering surface 25 terminates in a flat end portion 28 which is axially raised relative to the gasket forming surface 25. The axially raised surface 28 engages the flat underside of the stacking panel 15 to form a flash barrier to preclude inward flow of the mold material 21 during shaping. As pointed out briefly above, even though the outer margin of the mold material is unconfined, radial inward flow still occurs causing the undesirable flash. The present invention provides an annular relief groove 30 which opens axially and is disposed immediately adjacent the axially raised top panel engaging portion 28. The volume of this groove will be at least equal to the maximum volume of gasket material on the positive side of the tolerance. Stated in another manner, if the accuracy of depositing the gasket material 21 has been of the order of 35% of the total weight, the volume of the groove 30 should be at least suflicient to accommodate a volume of gasket material equal to of the total weight of the gasket material. The

specific volume may vary with the gasket material selected, cap size and related factors.

As the punch 24 approaches the final position shown in FIGS. 2 and 3, any gasket material 21 which is extruded or flashed by the panel engaging axially raised surface 28 Will be allowed to expand and hence be trapped in the annular groove 30 to form a raised head 31 which terminates at its inner margin in a flash free edge 32. The raised bead 31 and the main body of the gasket are joined through an axially and radially thin section represented by the heavy line 33. Accordingly, the raised bead at the inner margin assists in anchoring the main body of the gasket through the thin section to preclude tearing away and exposure of the coating on the shell. During molding at the above temperatures, the plasticizers dissolve the greater portion of the vinyl particles attaining a higher viscosity and accordingly the mass of gasket material 21 becomes form-maintaining. A known type of adhesive primer may be provided on the inner surface of the shell and causes a solvent action to increase the bond or union between the primer and plastomeric gasket material to provide good adhesion. The United States patents to Unger et al., No. 2,874,863, and Zipper, No. 2,841,304 adequately describe such a material.

Inasmuch as the closure may subsequently come into contact with foodstuffs which are acidic or basic, it is essential that the protective coating covering the metal in the shell be adequately protected against scratches throughout the manufacturing operation as well as after completed. Since the flash barrier 28 is axially raised and generally flat, scarring or scuffing of the coating on the shell is unlikely to occur during molding, and if it should occur will be covered by the thin section of compound 33 joining the raised bead and gasket proper.

After the molding operation is complete, the shell containing the molded gasket is given an additional heat treatment of from about 2 to 4 minutes to cause a more complete dissolution of the particles in the plasticizer. While this operation is ordinarily performed immediately after molding of the gasket, it can be performed by a subsequent and completely independent operation which is spaced in time from the molding operation. Such final curing of the gasket may be performed by passing the shell through an oven on a conveyor for time suflicient t heat the cap and compound to about 350-100 F,

The above described apparatus and method is used to form a novel molded ring within a closure shell. The ring is characterized by having a sharply defined inner margin which is flash free and may include a raised bead or anchoring portion. While a gasket groove has been shown in the drawing, it is obvious that the foregoing principles are applicable to the formation of a gasket on any shape of surface with or without a groove. Flash is avoided and closure seals manufactured in accordance with these principles may be produced at faster than predecessor types and the over-all quality of the finished product is particularly enhanced by the novel flash free molding technique.

Obviously, certain modifications and variations as hereinbefore set forth may be made without departing from the spirit and scope thereof. Therefore, only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A closure cap having a molded gasket formed in a flash free manner, said closure cap including a shell having a top panel joined to a skirt portion to form a gasket area, a layer of gasket material deposited in said area and overlying a portion of said skirt portion and said top panel, said gasket material having a flash free margin formed by the main body of said gasket material being joined to a flash film portion which is thin relative to said main body and said thin flash film portion termimating in an axially raised bead forming a sharp cutoff of said gasket material which is free of flash and the weight of which bead does not exceed 5% of the total weight of said gasket material.

2. A closure cap having a molded gasket which is formed in a flash free manner at least along one margin thereof, said closure cap including a shell having a top panel joined to a skirt portion thereby to form a gasket groove having a flat bottom, said flat bottom being joined to said top panel through a frusto-conical portion, a layer of gasket material in said groove having inner and outer peripheries, said gasket material in its finally shaped form being rounded at its outer periphery and tapering to a portion of reduced thickness at the inner periphery, said inner periphery having a raised bead formed inwardly of said tapering portion and radially inward of the junction of said frusto-conical portion forming one side of the gasket groove and said top panel, and joined thereto by a thin film to form a flash free cut-ofi portion.

References Cited UNITED STATES PATENTS 1,322,914 11/1919 Lorenz 215-40 2,327,454 8/1943 Punte 215-40 X 2,700,186 1/1955 Stover 215-40 X 3,110,409 11/1963 Chaplin 215-40 3,187,920 6/1965 Dorn 215-40 FOREIGN PATENTS 1,019,711 11/ 1952 France.

DONALD F. NORTON, Primary Examiner.

J E H R.- LECLA R, Examine 

1. A CLOSURE CAP HAVING A MOLDED GASKET FORMED IN A FLASH FREE CHAMBER, SAID CLOSURE CAP INCUDING A SHELL HAVING A TOP PANEL JOINED TO A SKIRT PORTION TO FORM A GASKET AREA. A LAYER OF GASKET MATERIAL DEPOSITED IN SAID AREA AND OVERLYING A PORTION OF SAID SKIRT PORTION AND SAID TOP PANEL, SAID GASKET MATERIAL HAVING A FLASH FREE MARGIN FORMED BY THE MAIN BODY OF GASKET MATERIAL BEING JOINED TO A FLASH FILM PORTION WHICH IS THIN RELATIVE 